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CAM2: and why Lab Impex bought a licence

CAM2: and why Lab Impex bought a licence. Morgan Jones AWE. What is a CAM and what does it do?. CAM = Continuous Air Monitor Machining radioactive materials risks dust entering external atmosphere and being inhaled Pump air at 40 litres/minute Trap dust on standard 25mm diameter filter

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CAM2: and why Lab Impex bought a licence

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  1. CAM2: and why Lab Impex bought a licence Morgan Jones AWE

  2. What is a CAM and what does it do? • CAM = Continuous Air Monitor • Machining radioactive materials risks dust entering external atmosphere and being inhaled • Pump air at 40 litres/minute • Trap dust on standard 25mm diameter filter • 239Pu and 235U are αemitters (5.2MeV, 4.4MeV) • Thin silicon detector 4.5mm away, opposite filter

  3. Penetration of radiation CAMs exist to warn of potential biological damage due to inhalation of radioactive airborne dust particles. Damage is proportional to energy deposited per unit path length: • α: Stopped by sheet of paper or epidermis • β: Stopped by 3mm of aluminium or Perspex/Lucite • γ: Quite hard to stop, inches of lead may not be enough Thus, although an alpha emitter may be innocuous externally, ingestion or inhalation is very dangerous.

  4. AWE outline design specification • Primarily α detection, but β detection added at commercial request • Send robust signals down existing cabling • Retain AWE’s familiar interface; minimise new bells & whistles • Make the hardware modular, use generic components, keep it simple • Radon…

  5. CAMs live or die by radon…

  6. But peak proportions change with time

  7. Outline radon compensation requirement • 256 channel spectrometry. Original AWE CAM used Regions Of Interest with radon algorithm tailored to each building (to match proportions of U and Th series in the building materials) • Automated curve fitting – one size fits all • Keep the algorithm simple • Assembler rather than high-level language

  8. Exponential curve fitting

  9. Curve fitting • Curves caused by random alpha path lengths across that 4.5mm air gap • Traditional technique fits and strips all three daughter peaks sequentially starting from highest energy • But air gap compensation allows all three peaks to use the same value of exponential, enabling a single curve fit

  10. Release detection • Traditional technique subtracts all three peaks and treats entire residual as release – very sensitive to curve fitting errors • AWE technique tests for statistical anomalies – automatically ALARP*, and resistant to radon jumps caused by opening doors * As Low As Reasonably Practicable

  11. Release detection (from early type test)

  12. Summary • Drop-in replacement for existing AWE CAM (500 ordered in March 2012) • One size fits all • Statistical release detection confers enhanced immunity to abrupt radon changes

  13. Why Lab Impex bought a licence… UK Patent 1011982.4 (filed July 2010) covers: • Air gap compensation and consequent simplified curve fitting • Channel by channel statistical testing • Adjacent channel testing

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